Surface mount filter device

ABSTRACT

A surface mount filter device is provided having a device body with a plurality of terminations located thereon. Capacitors and inductors are located on the same chip to create a variety of LC filters, such as LPF, HPF, BPF and BRF, or combinations of these options, as well as LC resonator structures. The chip is preferably built by thin film technology, which allows a considerable reduction in component or circuit size. The device body is constructed having a rigid insulative substrate to which a first conductive pattern having one or more first capacitor plates is applied. A dielectric is located over the first conductive pattern, and itself supports a second conductive pattern defining the opposed capacitor plates. One or more layers of insulative polymer are located above the dielectric layer, and have conductor channels in which conductive material is located. The conductive material in the conductive channels forms the coil of the on-chip inductor. A sealing cover, such as glass or a planar polymeric sheet, is located above the polymeric insulative layers.

CROSS-REFERENCE TO A RELATED APPLICATION

This application is based on a Provisional Application filed Oct. 15,1997 and having Ser. No. 60/062,364.

BACKGROUND OF THE INVENTION

The present invention relates generally to small electronic componentsadapted to be surface mounted on a larger circuit board. Moreparticularly, the invention relates to a surface mount filter device foruse in a variety of applications.

Surface mount components are often rectangular, and very small. Forexample, the component may have length and width dimensions of less than1/10 of an inch. Generally speaking, the component body will includeside terminations compatible with mass production soldering techniques.

As known by those skilled in the art, filters are often created byvarious combinations of electronic components. The components may bediscrete, or combined on a chip. The component values, and theirarrangement, determines the frequencies that are passed by the filter.For example, low pass filters (LPF), high pass filters (HPF), band passfilters (BPF) and band reject filters (BRF) can be made in this manner.

A need exists for novel filter devices that are compatible with surfacemount techniques.

SUMMARY OF THE INVENTION

The present invention recognizes various disadvantages of prior artconstructions and methods. Accordingly, it is an object of the presentinvention to provide novel surface mount components.

It is a more particular object of the present invention to providevarious novel structures for a surface mount filter device.

It is a further object of the present invention to provide small filterdevices particularly adapted for use in various applications.

It is also an object of the present invention to provide novelmethodology for the production of a filter device.

Some of these objects are achieved by a surface mount filter devicecomprising a device body having a plurality of electrical terminationslocated thereon. The device body includes an insulating substrate havinga top surface and a bottom surface. At least one first conductivepattern in the form of a first capacitor plate is defined on a topsurface of the substrate. A dielectric layer is located on top of theconductive pattern. A second conductive pattern, defining at least onesecond capacitor plate in registry with said first capacitor plate, islocated on the dielectric layer. The second conductive pattern furtherdefines at least a portion of an inductor coil.

In exemplary embodiments, one or more layers of insulative polymer, suchas polyimide, are located above the dielectric layer. The insulativelayers preferably define a conductor channel in registry with theportion of the inductor coil of the second conductor pattern. Aconductor located in the conductor channel completes the inductor coil,and/or enhances its thickness to a desired value. An insulative coverlayer, which may be a polymeric sheet material or a rigid insulativematerial depending on the embodiment, is preferably disposed above theinsulative layers.

Other objects, features and aspects of the present invention areprovided by various combinations and subcombinations of the disclosedelements, as well as methods of practicing same, which are discussed ingreater detail below.

BRIEF DESCRIPTION OF THE DRAWINGS

A full and enabling disclosure of the present invention, including thebest mode thereof, to one of ordinary skill in the art, is set forthmore particularly in the remainder of the specification, includingreference to the accompanying drawings, in which:

FIG. 1 is a diagrammatic representation showing a filter device of thepresent invention installed on a circuit board as it may appear in use;

FIG. 2 is a schematic diagram of one preferred circuit arrangement in afilter device of the present invention;

FIG. 3 is an enlarged perspective view of the filter device of FIG. 1;

FIG. 4 is a cross sectional view as taken along line 4-4 of FIG. 3;

FIG. 5 is a plan view taken along line 5--5 of FIG. 4 showing onepreferred conductor layout in a filter device of the present invention;

FIGS. 6A through 6F are plan views showing sequentially formed layers toproduce the conductor layout of FIG. 5;

FIG. 7 is a plan view taken similar to FIG. 5 showing an alternativeconductor layout in a filter device of the present invention;

FIGS. 7A through 7F are plan views showing sequentially formed layers toproduce the conductor layout of FIG. 7;

FIG. 8 is a flow chart showing preferred methodology for the manufactureof a surface mount filter as in FIG. 3;

FIG. 9 is a flow chart similar to FIG. 8 showing preferred methodologyfor producing a flip chip component;

FIG. 10 is a perspective view of a resonator device constructed inaccordance with the present invention;

FIG. 11 is a schematic diagram of one preferred circuit arrangement inthe resonator device of FIG. 10;

FIG. 12 is a plan view showing one conductor pattern that may beutilized to produce a resonator as in FIG. 10;

FIG. 13 is a plan view showing another conductor pattern that may beutilized to produce a resonator as in FIG. 10;

FIGS. 14A through 14F are plan views showing sequentially formed layersto produce the conductor layout of FIG. 13; and

FIG. 15 is a flow chart showing preferred methodology for themanufacture of a surface mount resonator as in FIG. 13.

Repeat use of reference characters in the present specification anddrawings is intended to represent same or analogous features or elementsof the invention.

DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS

It is to be understood by one skilled in the art that the presentdiscussion is a description of exemplary embodiments only, and is notintended as limiting the broader aspects of the present invention, whichbroader aspects are embodied in the exemplary constructions.

The present invention provides various surface mount devices having amultilayer structure to achieve desired filter arrangements. Forexample, capacitors and inductors are located on the same chip to createa variety of LC filters, such as LPF, HPF, BPF and BRF, or combinationsof these options, as well as LC resonator structures. The chip ispreferably built by thin film technology, which allows a considerablereduction in component or circuit size.

According to an important aspect of the invention, the multiple layerscan include capacitance layers, inductance layers and a layer combiningboth. The filter of the present invention can be employed in varioushigh frequency applications (e.g., above 100 MHz) for cellular phones,paging systems, wireless LANs, and other wireless communication systems.

Referring now to FIG. 1, filter 10 is shown as it may appear whensurface mounted to a printed circuit board 12. Often, circuit board 12may be made from a low-temperature organic material, with the solderoften being a low temperature eutectic solder applied by wave, reflow,vapor phase or manual soldering techniques.

As shown, filter 10 includes a device body 14 having a plurality ofterminations 16, 18, 20 and 22 thereon. Terminations 16 and 18 areattached to board 12 at respective mounting pads, such as pad 24.Conductive traces, such as trace 26, may be defined on the top surfaceof circuit board 12 using known microstrip techniques. As shown, theconductive traces extend from a respective mounting pad to provideelectrical communication with other circuitry. In this case, termination16 is the device input, with the device output being termination 18.Terminations 20 and 22 are attached to a single mounting pad 28 which iselectrically connected to ground plane 30 through vias 32 and 34.

FIG. 2 illustrates one filter arrangement, such as a LPF, including aninductor coil 36 and a plurality of capacitors, indicated at 38, 40 and42. In this case, inductor coil 36 and capacitor 40 are connected inparallel between input termination 16 and output termination 18.Capacitors 38 and 42 are connected between ground and the respectiveterminations 16 and 18.

Referring now to FIG. 3, device body 14 will often be rectangular,defining a longer length dimension and a shorter width dimension.Preferably, device body 14 is sized to conform to a standard size forother small surface mount components, such as multilayer ceramiccapacitors. According to industry practice, the size of a such acomponent is generally expressed as a number "XXYY," with XX and YYbeing the length and width, respectively, in hundredths of an inch. Atypical size under this practice is 0805.

Referring to FIG. 4, device body 14 includes an insulating substrate 44,which is preferably formed of alumina or a like rigid material. Forexample, a glazed alumina substrate may be utilized for this purpose. Aplurality of layers alternately provide patterned conductors asnecessary to achieve the desired filtering function. A sealing cover 46,which is preferably made from glass, glass-ceramic, alumina or a similarrigid insulative material, is located above the alternating layers. Asuitable polymer material, such as polyimide, can be used as the sealingcover in some embodiments. This is particularly desirable in flip chipversions of the device.

FIG. 5 shows the circuit arrangement of FIG. 2 as it may appear whenbuilt into a filter of the present invention. As can be seen, capacitors38, 40 and 42 are formed under the layer in which most of inductor coil36 is located. As will be apparent to one skilled in the art, each ofthe capacitors 38, 40 and 42 is actually formed as two capacitors thatare serially connected by a common bottom electrode plate. It can beseen that respective ends of the upper layer portion of inductor coil 36register with conductors underneath to provide electrical communicationwith terminations 16 and 18.

The manner in which the conductors of the filter device are formed willnow be described with reference to FIGS. 6A through 6F. As shown in FIG.6A, a first conductive pattern, here defining a plurality of capacitorplates 48, 50 and 52 is formed on the top surface of substrate 44.Generally, capacitor plates 48, 50 and 52 will be very thin and may bedefined using known photolithographic techniques. In a preferredembodiment, capacitor plates 48, 50 and 52 are formed of aluminum havinga thickness of about 2 microns. This layer can be referred to as "PadI."

Referring now to FIG. 6B, a dielectric layer 54, such as SiNO or SiO₂,is next deposited coextensive with the top surface of substrate 44. As aresult, dielectric layer 54 will cover the first conductive pattern onsubstrate 44. In a preferred embodiment, a dielectric thickness of about1.65 microns is applied in this manner.

As shown in FIG. 6C, a second conductive pattern is then formed,preferably by photolithography, above dielectric layer 54. As can beseen, the second conductive pattern defines capacitor plate structures56a-56b, 58a-58b and 60a-60b overlying respective capacitor plates 48,50 and 52. The second conductive pattern further defines inductor coilinterconnects, indicated at 62 and 64. This layer, which may have aconductor thickness of about 2 microns in preferred embodiments, may bereferred to as "Pad II."

At least two insulative layers, which may be made from polyimide or asimilar polymeric material, are disposed over the second conductivepattern. For example, a photoimageable polyimide may be practiced. Theembodiment of FIG. 4 includes two polymer layers, respectively indicatedas 66 and 68. These layers, which are respectively shown in FIGS. 6D and6F, may be referred to as "Poly I" and "Poly II".

The polymer insulative layers define conductor channels in register withcertain portions of underlying thin film conductors. The conductorchannels are filled, such as electroplating, to thicken the inductorcoil pattern, as well as to provide connections to terminations on theside of the device. For example, polymer layers of at least 15 microns,and preferably about 25 microns, can be utilized to provide conductorsof like thickness.

As can be seen in FIG. 6D, the conductor channel overlying interconnect62 is discontinuous, leaving a short stub portion 70 and a via conductor72. As a result, an insulative bridge is provided at the location whereturns of the overlying coil pattern will cross. Electrical connection tothe coil is maintained through thin layer interconnect 62.

FIG. 6E shows the thin layer pattern ("Pad III") that is next formedover layer 66. As shown, the pattern is that of the top layer inductorcoil. Final polymer layer 68 (FIG. 6F) defines a conductor channel inregister with this pattern in which a thickened conductor is provided byelectroplating or other suitable means as described above.

One skilled in the art will appreciate that various alternative layerconstructions, as well as various circuit arrangements, can be achievedaccording to the teachings of the present invention. For example, FIG. 7illustrates an alternative filter 10' wherein the coil pattern 36' islocated below the top conductor layer. This embodiment may beparticularly useful in higher frequency applications, such as 1900 or2400 MHz. The embodiment of FIG. 5, in contrast, may be particularlyuseful in lower frequency applications, such as 900 MHz.

One or more interconnects, such as interconnect 74, may be located onthe layer immediately below the sealing cover. Interconnect 74 functionsto electrically connect one end of coil pattern 36' with the nodebetween capacitors 40' and 42'.

The various layers of this embodiment can be easily understood withreference to FIGS. 7A through 7F.

As shown in FIG. 7A, the first conductive pattern is located on the topsurface of substrate 44', here defining a plurality of capacitor plates48', 50' and 52'. Next, as shown in FIG. 7B, a dielectric layer 54 isdeposited coextensive with the top surface of substrate 44'. A secondconductive pattern as shown in FIG. 7C ("Pad II") is then formed abovedielectric layer 54'. It can be seen that this conductive patterndefines capacitor plate structures 56a'-56b', 58a'-58b and 60a'-60b'overlying respective capacitor plates 48', 50' and 52'. The secondconductive pattern further defines much of inductor coil 36'.

Referring now to FIG. 7D, the next layer is an insulative layer 66' ("Poly I") of a suitable polymeric material as described above. Conductorchannels in layer 66' expose portions of the second conductive patternwhich may be filled, such as by electroplating, to enhance the conductorthickness. As shown in FIG. 7E, a further insulative layer 68' is thenapplied over layer 66' and the enhanced thickness conductors located inthe conductor channels thereof.

As shown in FIG. 7F, interconnect element 74 is applied as a thirdconductive layer above the surface of insulative layer 68'. Viaconductors 76 and 78 may be provided in the Poly II layer to permitelectrical communication with interconnect elements 74. The device maythen be covered by an appropriate sealing cover such as that illustratedin relation to the previous embodiment.

Often, filter devices of the present invention will be one of manymanufactured in a larger sheet. The terminations may be applied afterdicing of the larger sheet into individual components. A preferredmanufacturing process for a component covered by glass or the like isshown in FIG. 8. Similarly, FIG. 9 illustrates a preferred manufacturingprocess for a flip chip component covered, for example, with polyimideor another such polymer.

Thus, referring to FIG. 8, production of a glass-covered componentbegins by appropriate cleaning of the substrate. After deposition ofmetal on the substrate, metal lines of the first conductive pattern aredefined. A dielectric layer is disposed over the first conductivepattern, which is then covered with another layer of metal. Aninsulating layer of polymer is then applied in which appropriateconductor channels are defined. Metal is plated in the conductorchannels to enhance the conductor thickness. A further metal layer isthen disposed over the insulating layer, in which metal lines aredefined. A further insulating layer of polymer is applied, in whichconductor channels are then defined. An additional layer of metalplating is applied before application of the sealing cover.

At this point, a multiplicity of devices have been produced in a largersheet. The larger sheet is then diced in both X and Y directions toyield individual components. The individual components are terminated toform surface mount devices by termination definition, followed byapplication of solder.

Referring to FIG. 9, it can be seen that many steps in the production ofa flip chip component are similar to the production of a coveredcomponent. After the second "metal plating" step, however, a furtherinsulating layer is applied. Termination pads are defined on the surfaceof the insulating layer. After bump plating, the sheet is diced in bothX and Y directions to form the individual components. Finally, solder isapplied to the individual components.

FIG. 10 illustrates a resonator device 100 constructed in accordancewith the present invention. Unlike the filters shown above, resonator100 has only two terminations, indicated at 102 and 104. Referring nowto FIG. 11, resonator 100 preferably includes at a capacitor 106 and aninductor 108. Capacitor 106 and inductor 108 are connected in parallelto resonate at the desired frequency.

FIG. 12 illustrates the conductor layout in one resonator embodiment ofthe present invention. As shown, the "inductor" is formed by acircuitous conductor element 110. Capacitor 106 is formed as the seriescombination of two capacitors produced by lower capacitor plate 112 andtwo overlying plates 114a-b. Plates 114a-b are connected to a respectiveof terminals 102 and 104.

As one skilled in the art will recognize, the arrangement of FIG. 12 maybe made according to the methodology described above. It will beappreciated that such techniques also permit more elaborate arrangementsto be readily produced, one of which is shown in FIG. 13.

In particular, FIG. 13 shows a resonator 100' having terminations 102'and 104'. A capacitor 106' is formed as described above. In this case,however, the inductor, designated 108', has a plurality of turns forenhanced inductance. In particular, a lower layer spiral 116 (FIG. 14D)and an upper layer spiral 118 (FIG. 14F) are connected together througha via 120 (FIG. 14E).

FIGS. 14A through 14F show the formation of individual layers to produceresonator 100'. Referring first to FIG. 14A, a first patterned conductorin the form of a lower capacitor plate 122 is formed on a substrate 124.A dielectric layer 126, coextensive with the upper surface of substrate124, is then applied as shown in FIG. 14B. Next, as shown in FIG. 14C, asecond patterned conductive layer is applied. The second patternedconductive layer includes portions 128a and 128b forming upper capacitorplates. As described above with respect to other embodiments, thecapacitor 106' is actually the equivalent capacitor realized by a pairof actual capacitors connected in series. The lower coil portion 116 islocated adjacent to the capacitor electrodes, as shown.

Referring now to FIG. 14D, a first layer of insulative polymer ("PolyI") is then located above the second conductive pattern. Channels areformed in insulative layer 130 to expose portions of the secondconductive pattern as shown. The channels are filled with additionalconductive material to enhance the conductor thickness at theselocations. Another insulative layer 132 is then applied, as shown inFIG. 14E, in a manner that exposes via 120.

Referring now to FIG. 14F, a third conductive pattern may then be formedon top of insulative layer 132. An additional insulative layer 134 isthen provided, having conductor channels in registry with upper layerspiral 118. The conductor channels are filled with additional conductivematerial to enhance the conductor thickness as described above. Themethodology of producing a resonator as described is also shown in theflow diagram of FIG. 15.

Some of the techniques by which conductors are formed in filter devicesof the present invention may be the same as, or analogous to, thetechniques described in U.S. Pat. No. 5,363,080 to Breen. Accordingly,this patent is incorporated herein by reference.

It can be seen that the present invention provides various novel filterstructures adapted for use as surface mount components. While preferredembodiments of the invention have been shown and described,modifications and variations may be made thereto by those of ordinaryskill in the art without departing from the spirit and scope of thepresent invention. In addition, it should be understood that aspects ofthe various embodiments may be interchanged both in whole or in part.Furthermore, those of ordinary skill in the art will appreciate that theforegoing description is by way of example only, and is not intended tobe limitative of the invention, which is further described in theappended claims.

What is claimed is:
 1. A surface mount filter device comprising a devicebody including a plurality of electrical terminations located thereon,said device body including:an insulating substrate having a top surfaceand a bottom surface; a first conductive pattern in the form of at leastone first capacitor plate defined on a top surface of the substrate; adielectric layer located on top of the conductive pattern; a secondconductive pattern located on said dielectric layer, said secondconductive pattern defining at least one second capacitor plate inregistry with said first capacitor plate to produce a capacitor device,said second conductive pattern further defining at least a portion of aninductor coil; a first layer of insulative polymer located above thedielectric layer and a first layer conductor channel in registry withsaid portion of said inductor coil, said first layer conductor channelcontaining a conductive material; and an insulative cover layer.
 2. Asurface mount filter device as set forth in claim 1, further comprisinga second layer of insulative polymer located above said first layer ofinsulative polymer.
 3. A surface mount filter device as set forth inclaim 2, wherein said second layer of insulative polymer defines asecond layer conductor channel containing conductive material definingan inductor coil.
 4. A surface mount filter device as set forth in claim2, wherein said second layer of insulative polymer defines a secondlayer conductor channel containing conductive material defining aninterconnect for said first layer conductor channel.
 5. A surface mountfilter device as set forth in claim 1, wherein said insulative polymeris a photoimageable polyimide.
 6. A surface mount filter device as setforth in claim 1, wherein said sealing cover is formed from a planarsheet of insulative polymeric material.
 7. A surface mount filter devicecomprising a device body including a plurality of electricalterminations located thereon, said device body including:an insulatingsubstrate having a top surface and a bottom surface; a first conductivepattern in the form of at least one first capacitor plate defined on atop surface of the substrate; a dielectric layer located on top of theconductive pattern; a second conductive pattern located on saiddielectric layer, said second conductive pattern defining at least onesecond capacitor plate in registry with said first capacitor plate toproduce a capacitor device, said second conductive pattern furtherdefining at least a portion of an inductor coil; a first layer ofinsulative polymer located above the dielectric layer and a first layerconductor channel in registry with said portion of said inductor coil,said first layer conductor channel containing a conductive material; andan insulative cover layer, wherein said dielectric layer comprises athin layer dielectric material selected from a group consisting of SiNOand SiO₂.
 8. A surface mount filter device comprising a device bodyincluding a plurality of electrical terminations located thereon, saiddevice body including:an insulating substrate having a top surface and abottom surface; a first conductive pattern in the form of at least onefirst capacitor plate defined on a top surface of the substrate; adielectric layer located on top of the conductive pattern; a secondconductive pattern located on said dielectric layer, said secondconductive pattern defining at least one second capacitor plate inregistry with said first capacitor plate to produce a capacitor device,said second conductive pattern further defining at least a portion of aninductor coil; a first layer of insulative polymer located above thedielectric layer and a first layer conductor channel in registry withsaid portion of said inductor coil, said first layer conductor channelcontaining a conductive material; and an insulative cover layer, whereinsaid sealing cover is formed from a rigid insulative material selectedfrom a group consisting of glass, glass-ceramic and alumina.
 9. Asurface mount filter device comprising a device body including aplurality of electrical terminations located thereon, said device bodyincluding:an insulating substrate having a top surface and a bottomsurface; a first conductive pattern in the form of at least one firstcapacitor plate defined on a top surface of the substrate; a dielectriclayer located on top of the conductive pattern; a second conductivepattern located on said dielectric layer, said second conductive patterndefining at least one second capacitor plate in registry with said firstcapacitor plate to produce a capacitor device, said second conductivepattern further defining at least a portion of an inductor coil; a firstlayer of insulative polymer located above the dielectric layer and afirst layer conductor channel in registry with said portion of saidinductor coil, said first layer conductor channel containing aconductive material; and an insulative cover layer, wherein said atleast one first capacitor plate is not directly connected with any ofsaid terminations.
 10. A surface mount filter device comprising a devicebody including a plurality of electrical terminations located thereon,said device body including:an insulating substrate having a top surfaceand a bottom surface; a first conductive pattern in the form of at leastone first capacitor plate defined on a top surface of the substrate; adielectric layer located on top of the conductive pattern; a secondconductive pattern located on said dielectric layer, said secondconductive pattern defining at least one second capacitor plate inregistry with said first capacitor plate to produce a capacitor device,said second conductive pattern further defining at least a portion of aninductor coil; a first layer of insulative polymer located above thedielectric layer and a first layer conductor channel in registry withsaid portion of said inductor coil, said first layer conductor channelcontaining a conductive material; and an insulative cover layer, whereineach of said second capacitor plates comprises a pair of secondcapacitor electrodes disposed over a respective at least one of saidfirst capacitor plates to produce a respective equivalent capacitorelement.
 11. A surface mount filter device as set forth in claim 10,wherein said first conductive pattern defines at least three of saidfirst capacitor plates, each being superposed by a respective pair ofsaid second capacitor electrodes to produce at least three of saidequivalent capacitor elements.
 12. A surface mount filter device as setforth in claim 11, comprising at least four of said terminations locatedon lateral sides of said device body.
 13. A surface mount filter deviceas set forth in claim 12, wherein:a first equivalent capacitor elementis electrically connected between a first termination and a secondtermination; a second equivalent capacitor element is electricallyconnected between said first termination and a third termination; and athird equivalent capacitor element is electrically connected betweensaid second termination and a fourth termination.
 14. A surface mountfilter device as set forth in claim 13, wherein said inductor iselectrically connected between said first termination and said secondtermination.